DEAR DR. DONOHUE: I once worked as an orderly in a hospital’s emergency room. During the winter I saw two people brought in with hypothermia, and one died.

I run outdoors, and this winter has been very cold. I wonder if I could be putting myself in danger of hypothermia. Will you write something about this? Thanks. — R.M.

ANSWER: An accepted criterion for hypothermia is a core body temperature of 95 F (35 C) or lower. Core temperature is the temperature of internal organs — heart, liver, lung, brain. Some define it as the temperature of the blood as it leaves the heart. Special rectal probes are one way of obtaining core temperatures.

A core temperature from 90 to 95 F (32 to 35 C) is mild hypothermia. People with mild hypothermia shiver vigorously. Muscle contractions cause shivering, and muscle contractions generate heat. A person’s skin is cold and white. Rapid rewarming with blankets and a change of clothes is the standard treatment. Immersion in warm water is another acceptable treatment. Moderate hypothermia is a core temperature of 82 to 90 F (28 to 32 C). Shivering diminishes, speech becomes slurred, the heart beats slowly, and people are confused. Severe hypothermia is a core temperature below 82 F (28 C). Shivering stops, the skin is cold and stiff, blood pressure is low, and breathing has slowed. People are often unresponsive.

All hypothermia is an emergency and should be treated in a hospital where there are facilities for rapid rewarming and where there is equipment that monitors organ function. Moderate and severe hypothermia require professional attention. Even then, the mortality rate from severe hypothermia approaches 40 percent. If an affected person is stranded in a remote area, the best that can be done is to warm that person with a change of clothing, wrap him or her in blankets and take any measures available to raise that person’s temperature.

Exercising in cold weather is all right if you are sensible about it. In extreme cold, you should stay inside. Otherwise, dress in layers. Long underwear made from lightweight polyester or polypropylene wicks sweat away from the skin and serves as the best material for the first layers. Over the underwear, a layer of fleece or wool clothing serves as heat insulation. An outer layer of material that allows moisture to transfer to the air but repels wind and water is best. The head should be covered. A ski mask is good protection. Gloves or mittens should be worn.

DEAR DR. DONOHUE: I’m a male, 51 years old, and in good shape. I eat healthy and get lots of rest. I exercise. My doctor says my cholesterol is still high, so I take 40 mg of Lipitor daily.

My question is this: I read that taking a statin drug (Lipitor) can prevent muscle growth. I work out three times a week, with 15 minutes of cardio exercise and 45 minutes of weight training. In more than two years, I have seen little muscle growth. My muscles are better toned than they were. Can I cut my Lipitor in half and still get benefits from it? — J.D.

ANSWER: I have never seen in print or heard that statins prevent muscle growth. They can cause muscle pain. Statins lower cholesterol more effectively than just about any other intervention. Don’t decrease the dose of your medicine without consulting your doctor and without knowing what your current cholesterol level is.

Muscle growth occurs only by constantly presenting new challenges to the muscles. That entails gradual increase in the amount of weight you lift. Once you can perform three consecutive sets of 12 lifts, increase the poundage and cut back to three consecutive sets of eight lifts.

DEAR DR. DONOHUE: I walk or ride my bike daily for at least 45 minutes. If I walk for 45 minutes or ride my bike (a tricycle) for the same amount of time, which is more beneficial to me? — M.G.

ANSWER: They’re both beneficial to you, and you can choose the one you enjoy more.

You also can answer the question yourself. Which feels like more work to you? That’s called perceived exertion and is a valid way of determining exercise intensity.

Or you can count your pulse during and at the end of exercise. Which gets your pulse beating faster?

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from

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